The activation of human gene MAGE-1 in tumor cells is correlated with genome-wide demethylation.

Abstract

Human gene MAGE-1 encodes tumorspecific antigens that are recognized on melanoma cells by autologous cytolytic T lymphocytes. This gene is expressed in a significant proportion of tumors of various histological types, but not in normal tissues except male germ-line cells. We reported previously that reporter genes driven by the MAGE-1 promoter are active not only in the tumor cell lines that express MAGE-1 but also in those that do not. This suggests that the critical factor causing the activation of MAGE-1 in certain tumors is not the presence of the appropriate transcription factors. The two major MAGE-1 promoter elements have an Ets binding site, which contains a CpG dinucleotide. We report here that these CpG are demethylated in the tumor cell lines that express MAGE-1, and are methylated in those that do not express the gene. Methylation of these CpG inhibits the binding of transcription factors, as seen by mobility shift assay. Treatment with the demethylating agent 5-aza-2'-deoxycytidine activated gene MAGE-1 not only in tumor cell lines but also in primary fibroblasts. Finally, the overall level of CpG methylation was evaluated in 20 different tumor cell lines. It was inversely correlated with the expression of MAGE-I. We conclude that the activation of MAGE-1 in cancer cells is due to the demethylation of the promoter. This appears to be a consequence of a genome-wide demethylation process that occurs in many cancers and is correlated with tumor progression.

Subtelomeric DNA hypomethylation is not required for telomeric sister chromatid exchanges in ALT cells

“…This is not the case for cancer-linked hypomethylation of pericentromeric satellite 2 DNA, which is significantly associated with global cancerlinked DNA hypomethylation (Weisenberger et al, 2005;Ehrlich, 2006). Deep genomic DNA demethylation in ALT tumor cells was further shown in our study by the expression of the cancer germline gene MAGE-A1, which was correlated earlier with genome-wide hypomethylation in tumors (De Smet et al, 1996;Cadieux et al, 2006). Alternatively, DNA hypomethylation in ALT cells could be related to their origin as most ALT cell lines derive from sarcomas.…”

“…A very good correlation was found between the level of Sat2/ Alu methylation and the average methylation level of D4Z4 and DNF92 subtelomeric sequences (Figure 5d). Profound genomic DNA demethylation in ALT cancer cells was further confirmed by the expression of the cancer germline gene MAGE-A1 (Figure 5c), the expression of which was correlated earlier with global genomic DNA demethylation in tumors (De Smet et al, 1996;Cadieux et al, 2006). Altogether, these data suggest that hypomethylation of subtelomeric sequences in ALT tumor cells results from the genome-wide DNA demethylation process often associated with tumorigenesis.…”

“…First, we measured Sat2 and Alu methylation levels in in vitro methylated genomic DNA and DNA isolated from cells treated with the DNA-demethylating agent 5-aza-2 0 -deoxycytidine ( Supplementary Figure 3a and b). Second, we correlated MethylLight-based analysis with M.SssI/dam 3 H-methyl incorporation ratio measurement for quantification of overall methyl CpG content in MZ2, LB188, LB23 and LB45 tumor cell lines and normal fibroblasts (De Smet et al, 1996) (Supplementary Figure 3c).…”

MAGE, BAGE and GAGE: tumour antigen expression in benign and malignant ovarian tissue

“…Our findings in benign ovarian pathological specimens were totally unexpected, with 11/25 lesions expressing MAGE-1 (Table 3). Of these benign lesions expressing MACE-I, inclusion cysts, serous cystadenomas and mucinous cystadenomas are considered putative precursor lesions, whereas fibromas are not (Table 4 (Weber et al, 1994;De-Smet et al, 1996;Mori et al, 1996;Shichijo et al, 1996). The study of MAGE-1 protein expression with anti-MAGE-1 monoclonal antibodies could provide further information as to the role of MAGE genes.…”

Cancer testis antigens expression in mesothelioma: role of DNA methylation and bioimmunotherapeutic implications

“…Furthermore, due to the demonstrated role of DNA methylation in regulating gene expression (Jones and Takai, 2001), and since promoter methylation is involved in the expression of MAGE genes in human melanoma (De Smet et al, 1996, 1999Sigalotti et al, 2002), we investigated the role of the DNA hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA-CdR) in regulating the differential distribution of CTA and their constitutive levels of expression in MM.…”